1. Field of Invention
The present invention relates to a method and an apparatus for entering a special mode in an integrated circuit (IC) or a logic circuit. More particularly, the present invention relates to a method and an apparatus for entering a special mode in an IC or a logic circuit after being reset.
2. Description of Related Art
Generally speaking, products such as displays and ICs must go through a shop test after being fabricated, so a special mode known as “engineering mode” must be designed. The “engineering mode” can be used to determine whether the products such as ICs or displays can work well or not, or to set the factory settings of the products. Under the consideration of protecting the normal operation of the products with the settings not being modified by clients or users, the special mode such as “engineering mode” is not commonly known.
FIG. 1 is a block view of a conventional apparatus for entering the special mode in the IC. One IC component is taken as an example for illustration herein. The IC component comprises original pins 100 and a special mode detecting pin 101. When it is intended to enter the special mode such as the “engineering mode”, the special mode detecting pin 101 is set to a logic high level or a logic low level, thus entering the special mode. However, a system factory usually does not use the special mode detecting pin 101 when purchasing IC components, and this additional pin which is not actually used by the system clients cause a burden for the system factories. Taking the using of a logic high level to enter the special mode as an example, system factories, when using the above IC components, must connect this special pin to ground. Thus, it's really inconvenience for the system factories to design the layout of the IC components on the circuit board. Most clients prefer to choose another IC with the same function but without the pins, which may cause loss of customers.
Directed to the above disadvantages of the conventional art as shown in FIG. 1, a solution is provided. FIG. 2 is a circuit diagram of another conventional apparatus for entering the special mode in the IC. Similarly, the IC circuit is taken as an example for illustration, in which the apparatus comprises a plurality of registers 200 and a logic circuit 201. The apparatus employs a plurality of original data bits data_1˜data_N of the IC to be set to a certain predetermined value through a program. After the setting value is stored in the registers 200, a logic circuit 201 is used to determine the IC to enter the special mode or not. However, this method may be wrongly used by clients. If the clients carelessly change the register to be the predetermined value, they may enter the special mode, thus causing an unsuspected function or an abnormal function of the IC.